1. Field of the Invention
The present invention relates generally to laundry washing machines and, more particularly, to a washing machine having an improved suspension system equipped with isolation damper units.
2. Description of the Prior Art
Laundry washing machines of the top-loading variety typically include a cabinet having a base, a four-sided housing secured to the base, and a top enclosure secured to the top of the housing which has a lid to provide access to a spin basket. The spin basket is rotatably mounted within an outer tub and is perforated to allow the wash water to be transferred into the outer tub during the centrifugal extraction or “spin” cycle. Such washing machines also include a drive assembly for controlling high-speed rotation of the spin basket as well as low-speed oscillatory movement of an agitator which is centrally located within the spin basket. Typically, the drive assembly includes an electric motor and a transmission that are mounted either to the cabinet base or a support structure. In turn, the support structure is mounted between the outer tub and the base of the cabinet by a suspension system that is adapted to absorb excessive vibration from unbalanced loads that may occur, for example, during the high speed spin cycle.
One example of a conventional suspension system for top-loading washing machines uses a dome-type pivot assembly between the support structure and the cabinet base that is anchored by a plurality of centering springs. The dome-type assembly typically includes a raised male dome segment centrally formed in the base and a corresponding female dome segment associated with the support structure. A low friction member, such as a plastic snubber ring, is disposed between the aligned dome segments. In some washing machines, one or both of the dome segments are coated, such as with a Teflon paint, to provide additional lubricity. The centering springs provide several functions including connecting the support structure and outer tub to the base, preventing rotation of the outer tub during the spin cycle, and allowing limited lateral movement of the outer tub while providing a means for automatically returning the outer tub to a centered position relative to the cabinet.
One particular concern with top-loading washing machines is the need to prevent excessive lateral movement of the outer tub caused by unbalanced loads of clothes in the spin basket during the spin cycle. Depending upon the amount and location of the load, it is possible to generate resonant frequencies that are capable of causing the outer tub to strike the sidewalls of the cabinet. In addition, the suspension system must also be able to accommodate rotation of the spin basket without transmitting the resultant vibration to the floor so as to prevent “walking” of the washing machine. In an attempt to address these concerns, many top-loading washing machines having the conventional spring-type suspension system are also equipped with a counterweighted ring at the top of the spin basket and/or an unbalance sensor that is operable for automatically de-energizing the drive assembly upon occurrence of an excessive out-of-balance condition. In addition, it is also conventional to install a layer of sound deadening material on the base of the cabinet to absorb a portion of the noise generated by such vibration.
In view of the above, there is a recognized need in the field of laundry washing machines to design and develop improved suspension systems that address the shortcomings of conventional spring-type systems which can be commercially produced at an economical cost.